Plasticization of gelatin with dialkoxypolyoxyalkylene glycols



U ed ta e m i LAsrrcrzArioN on GELATIN WITH DIALKOXY- POLYOXYALKYLENE GLYCOLS Kirby M. Milton, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application July 1, 1955 Serial No. 519,639

7 Claims. (Cl. 96-94) This invention relates to the 'plasticization of gelatin and of photographic gelatin emulsions by means of linear polyalkyl ethers.

Some materials such as glycerin or other polyols are known to plasticize gelatin probably because of either any statement in the art pointing out any unusual value of these glycols for gelatin plasticizing purposes.

One object of my invention is to provide gelatin coating compositions which give coatings having good fiexi properties or coatability. However, there has never been bilities. Another object of my invention is to plasticize photographic gelatin layers and photographic films containing those layers. A further object of my invention is to plasticize gelatin employed for photographic purposes without any adverse physical or sensitometric effects as might result from many currently known gelatin plastic1zers.

I have discovered that the above objects may be obtained by incorporating certain linear polyalkyl ethers in aqueous gelatin coating compositions. These ethers (dialkoxy polyoxyalkylene glycols) have the general formula: R O-- R O) -R where R R and R are saturated, aliphatic hydrocarbon groups and n' is an integer such as from 1 to 9 and preferably 3-4. R and R each may be either methyl or ethyl whereas R may be any saturated aliphatic hydrocarbon group either straight chain or branched and may be from 1 to 3 carbon atoms. One example of a material of this type which has been found 'to be useful in accordance with my invention is dimethoxytetraethylene glycol. It is desirable that the chain length of the polyether be enough that there is little or no loss by volatilization upon curing or keeping but not so large that the polyether is incompatible with gelatin when dry. In general 5-50% of plasticizer based on the weight of gelatin will be used but the optimum concentration may vary depending upon the particular polyether used. I have found that the use of the dialkoxy polyoxyalkylene glycols for the plasticization of gelatin possesses advantages over the polyoxyalkylene glycols themselves and the monoalkoxy polyoxyalkylene glycols .as will be illustrated by the following examples.

Example 1 Several gelatin sheets were prepared by coating out aqueous solutions of 8% of photographic gelatin and 2,860,980 Patented Nov. 18, 1958 ICC 1.6% of plasticizei' onto stripping type plates so that gelatin skins with dried thicknesses of 4 mils were o tained. The sheets were cured at F. and 70% R. H. until dry, stripped from the plates, slit to widths of 15 and conditioned to 70 F. and 20% R. H. Folding endurance was tested with an MIT Fold Tester using a tension of 1 kg. and jaws of 0.0155" radius of curvature with a separation of 0.01". Corresponding plasticized silver halide emulsion sheets were also prepared and tested. These tests resulted as follows:

MIT Folds at 20% R. H.

Percent 1 Plasticizer Gelatin Emulsion Skins Skins 0 N 36 20 Glycerin 99 42 Polyethylene Glycol 300 Methoxypolyethylene Glycol 350 120 45 Polyethylene Glycol 600 74 55 'Dimethoxytetraethylene Glycol 137 86 1 Parts per parts of gelatin.

Example 2 MIT Folds at 10% R. H.

Percent Plasticizer Polyethylene Glycol 300 Methoxypolyethylene Glycol 3 Polyethylene Glycol 600 Dimethoxytetraethylene Glycol Example 3 In a similar experiment the proportion of plasticizer was varied. Tests of those films resulted as follows:

Brittlencss at 10y}7 R. H.

Percent Plasticizer MIT Wedge Vise Folds None 0 35 .11 Glycerin 0 26 03 Dimethoxytetraethylene Glycol. 19 11 .02

Example 4 Films were prepared as described above using a positive type photographic emulsion with and Without dimethoxy tetraethylene glycol as a plasticizer. These films tested as follows:

Example 5 Various photographic emulsions (used to form Kodachrome film) were plasticized, and the resulting compositions were coated one over the other on cellulose acetate support. The resulting plasticized film was compared to a (Kodachrome) commercial photographic film similar in all respects save the lack of emulsion plasticizer in any of the layers. The resultsobtained wer'eas follows:

Films were coated from a photosensitive emulsion without plasticizer and with 20% and 30% of plasticizer respectively. The results obtained were as follows:

Brittleness MIT Vise at Folds at 14% 10% R. H. R. H.

No plasticizer 0 20% Dlmethoxytetraethylene Glycol 22 30% Dimethoxytetraethylene Glycol 25 Example 7 Strips of gelatin coatings were prepared in a series of preparations in the manner described above and plasticlzers in accordance with our invention and other similar compounds were used in both gelatin per se and in photographic emulsion compositions in the proportion of 20 parts per 100 parts of gelatin.

Plasticizer MIT Folds at 20% R1O-(R20)n-R3 R; n R; Gelatin Emulsion H 4 H 36 38 H 4 CZHS 48 50 CH: 3 CH3 57 64 OH; 4 CH; 62 85 PIN-N 0:000

The use of the dialkoxy ethers of polyoxyalkylene glycols in amounts up to 2030% or even more in gelatin coating compositions based on the weight of the gelatin was found to have no derogatory effect upon the properbeing plasticized entirely with the dialkoxy ethers of polyoxyalkylene glycols as described herein, may be plasticized with mixtures of one or more of those compounds with compatible glycols providing at least of the plasticizing material is the dialkoxy ether of a polyoxyalkylene glycol. As examples of mixtures which may be useful are compositions of dimethoxytetraoxyethylene glycol with glycerin, mixtures of dimethoxy tetraoxyethylene glycol with polytriethylene glycols or mixtures of dimethoxytrioxyethylene glycol with glycerin, triethylene glycol or ethylene glycol, providing the ether of the polyoxyalkylene glycol is at least 50% of the plasticizer employed in the gelatin composition.

Ordinarily the plasticizers will be added to the gelatin solution before the formation of a coating thereof. However, where a multi-layer coating is desired, plasticization can be accomplished by incorporating a plasticizer in ac cordance with my invention into one of the gelatin layers which plasticizer migrates into layers adjacent thereto. The plasticizers in accordance with my invention are free of the disadvantages common in gelatin plasticizers containing hydroxyl groups such as poor fiexibilities at low humidities,:,abnormally high moisture intake and I possibly undesirable sensitometric properties at high humidity.

Iclaim:

1. A plasticized gelatin composition comprising gelatin mixed with 550% of a plasticizing material at least 50% of which is a dialkoxypolyoxyalkylene glycol having the formula:

where R and R are alkyl groups of 1-2 carbon atoms, R is a saturated aliphatic hydrocarbon group from 1-3 carbon atoms and n is an integer within the range of 1-9.

2. A plasticized gelatin composition comprising gelatin and 20-30% of a plasticizing material at least half of which is a dialkoxy ether of a polyoxyalkylene glycol.

3. A plasticized gelatin composition comprising gelatin and 550% based on the gelatin of a plasticizer at least 50% of which is dimethoxytetraethylene glycol.

4. A plasticized gelatin composition comprising gelatin and 5-50% based on the gelatin of a plasticizer at least 50% of which is dimethoxytriethylenc glycol.

5. A plasticized gelatin-silver halide photographic emulsion which contains a plasticizer having the formula:

.' 7. A plasticized gelatin-silver halide photographic emulsion which contains a plasticizer having the formula:

R and R being alkyl groups of 1-2 atoms, R being a saturated aliphatic hydrocarbon group of 1-3 carbon atoms and n is 3-4.

References Cited in the file of this patent UNITED STATES PATENTS 2,240,469 Swan et al. Apr. 29, 1941 2,286,314 Seymour et al. June 16, 1942 2,684,909 Leekley et al July 27, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION he printed specification at error appears in t d that the said Letters It is hereby certified th ng correction an of the above numbered patent requiri t should read as corrected below.

Paten Column 4, line 63, for "ls-2 atoms" read l-2 carbon atoms Signed and sealed this 10th day of March 1959.i

ROBERT C. WATSON KARL H; AXLINE Attesting Oflicer Commissioner of Patents 

1. A PLASTICIZED GELATIN COMPOSITION COMPRISING GELATIN MIXED WITH 5-50% OF A PLASTICIZING MATERIAL AT LEAST 50% OF WHICH IS A DIALKOXYPOLYOXYALKYLENE GLYCOL HAVING THE FORMULA: 